Hey everyone! Canadian trailer-caterer-to-be here. I've been lurking for the last year or so as I have been planning but I'm just downright stuck on something that I cannot seem to be able to search out an answer for in the past threads.

I'm ordering a trailer from a manufacterer in Oregon (that builds lots of concession trailers). My choices are to insulate or not to insulate (only insulation they offer is the white styrofoam bead board stuff), then the trailer comes stock with ply, then I was going to have them line it with vinyl.

I did read on this thread that the white styro will soak up water like a sponge. In my trailer I will be doing full catering out of it... so my massive double oven, griddle, and 6 burners will be going full bore throughout the year, even in the winter. In my parts of Canada things rarely freeze up but they do hover just above freezing and boy oh boy does it rain here. Kinda like the climate in Seattle or Oregon coast. So with all that heat on the inside.... and all that wet cool air on the outside... ugh to what might collect inside my walls. Mold? Rotting walls/floors/ceilings? I am petrified with the "what if" scenarios. I know I need to have vapour barrier on the exterior walls of my house... but on the trailer?

So? What do you think? Pick the trailer up uninsulated and do the insulation, ply, and vinyl myself? (UGH)

Maybe the reason no one has posted about this issue is it's not an issue?

Styrofoam is Dow Chemical's brand name for their blue extruded insulation board. You may have that or something else often mistakenly called Styrofoam. White expanded polystyrene is often called that by error.

But that said I'll bet there have been many homes built in your area prior to vapor barriers being used. And last but not least ask the company your buying your trailer from. They will know if it's been a problem in the past.

Edit to add: Boat docks are built from the polystyrene around here and hold up well in the water year round even with freezing temps.

The warmer the air the more moisture it will hold. Your fan will suck air from the outside when it hits the warmer air in the trailer it will be drier. It's called relative humidity. If there's a small leak in your trailer wall the fan will suck drier air through the leak. In houses the problem is we put the humidity up to a comfortable level then we cook or shower that puts the humidity over the dew point so you have to exhaust it or it will condense anywhere there is a cooler surface or draft. I think the only time you would ever see a problem is, if you heated up the trailer, put a lot of steam in it with no exhaust then shut it down and sealed up the trailer.

Condensation only occurs on COLD surfaces, not warm. You never see a hot cup of coffee with condensation on it, only a cold ice drink. So the warm inside surfaces is not where the condensation will happen.

Next, the insulation you are referring to is the 'open cell' type or the bead type. Talk to the trailer manufacturer, I suspect they do not use this type of wall insulation for this very reason.

Next, the exhaust hood will vent the most air out drawing in the dryer cooler outside air. You will not have a problem.

If you are still unsure, install a vapor barrier on both sides of the outside wall.

Not on both sides, only on the inside and even that is not necessary. If you seal both inside and out all it takes is a small hole inside to let moisture through to the cold outside surface where it will condense if it is sealed the moisture has no place to go and you will have mold. I agree, you are looking for a problem that does not exist.

.... ... Trailer & food trucks that have been built or remolded on this forum has metal exterior sheeting with foam insulation (blue board ? & water proof), plywood interior sheeting with either SS or FRP on the inside surface. The metal exterior siding & the interior panel form moisture/vapor barriers on bother sides of the wall.

Even in house construction there is a moisture barrier under the exterior siding (old days tar paper; now plastic sheeting). ... Since water vapor moves from warm to cold surface, there should be a vapor barrier on the inside of wall studs to prevent moisture from entering the wall. ... This barrier might be part of the interior wall sheeting, if not it should be added.

For restaurant/kitchen construction, the interior moisture/vapor barrier is to prevent water from entering the wall and make wash down/cleaning/sanitation easier & simpler. ... thus old kitchens has glazed tile walls.

People who build metal boats have always dealt with this. No matter what sort of sheet or fiber insulation you put next to the metal surface, air will still be there and water can still condense. The only way to deal with this effectively and permanently is to have closed cell expanding urethane foam sprayed over the entire inside surface.

But with all the heat you're going to be generating in there, I can't imagine the inside surfaces will ever drop below the dew point. That would amaze me. Seems like a solution looking for a problem to me.

Even in house construction there is a moisture barrier under the exterior siding (old days tar paper; now plastic sheeting). ... Since water vapor moves from warm to cold surface, there should be a vapor barrier on the inside of wall studs to prevent moisture from entering the wall. ... This barrier might be part of the interior wall sheeting, if not it should be added. Tar paper isn't a moisture barrier it's a water barrier, yes in the south you would put plastic under the siding, it's hot and moist outside, dry and cool inside. In Canada that is reversed and the OP is in Canada.

Even in house construction there is a moisture barrier under the exterior siding (old days tar paper; now plastic sheeting). ... Since water vapor moves from warm to cold surface, there should be a vapor barrier on the inside of wall studs to prevent moisture from entering the wall. ... This barrier might be part of the interior wall sheeting, if not it should be added. Tar paper isn't a moisture barrier it's a water barrier, yes in the south you would put plastic under the siding, it's hot and moist outside, dry and cool inside. In Canada that is reversed and the OP is in Canada.

And a vapor barrier on the inside wall when it is warm & moist inside and COLD outside in the WINTER just like Canada. The problem is you don't want water collecting inside of the wall no matter what the source is or which direction vapor will be traveling.

Won't meet the building code up here. Vapor barrier both sides and the wall won't be dry. If you do it on new construction the moisture in the wood alone will cause mold. Any moisture that does get through the vapor barrier will not have enough air to take it away. The only way to keep it dry is spray foam.

And by the way, before we had plastic vapor barriers we didn't have mold, moisture isn't the problem, trapped moisture is. The wind used to blow through the houses and take the moisture with it. We had to use humidifiers to add moisture so we could breath. Once the houses were sealed just cooking and showers created a problem then we had to invent the HRV.

Won't meet the building code up here. Vapor barrier both sides and the wall won't be dry. If you do it on new construction the moisture in the wood alone will cause mold. Any moisture that does get through the vapor barrier will not have enough air to take it away. The only way to keep it dry is spray foam.

Vapor is the least of most people's wall problem, but trapped moisture is. This is the requirement for drain holes (masonry walls) or moisture/vapor barriers under siding; and for the building owner to investigate & stop the infiltration of the water. ... Air in a wall is a sign of a drafty wall and making insulation ineffective. Wet lumber or 'green' lumber should never be used in wall construction. Use kiln dried and properly store it onsite to prevent it from getting wet. Then moisture from the lumber should not be a problem once erected into the wall assembly.

You are attempting to debate a non-issue in food trailer & truck kitchen construction. Metal exterior wall and FRP interior wall = moisture/vapor barrier on both sides of the wall. If blue board or foam insulation is used, than another moisture/vapor barrier in the middle of the wall.

Note also that you are going to have a great deal of air circulation in there due to exhaust fans (or you will sweat and choke, I don't care how cold it is outside). We move about 400 cfm and our fans are pretty lame. These guys with the big mushroom fans are moving 1000-1200 CFM which is a phenomenal amount of air. Mold and air circulation don't mix...

Actually if I were really phobic about mold in the walls I might not insulate, I might drill a lot of holes all over. =^) Interesting thread really, I never thought about this.

I know the OP won't have problems. My problem began when you gave him bad information (vapor barrier both sides) and then argued the point even though you are wrong. You want to see how wrong, go to the link and learn.http://www.buildingscienc...tanding-vapor-barriers

I know the OP won't have problems. My problem began when you gave him bad information (vapor barrier both sides) and then argued the point even though you are wrong. You want to see how wrong, go to the link and learn. http://www.buildingscienc...tanding-vapor-barriers

I didn't give him bad information because I know the exhaust fan will pull out any latent water vapor that may be in the air as stated in your above reference due to air flow and pressure differences. Therefore, vapor is irrelevant; the use of additional vapor barrier is irrelevant. ... I further know the actual wall construction used in food trailer & trucks in fact forms moister/vapor barrier on both side of the wall as well as in many cases in the middle of the wall too. The problem faced by the owners of a food trailer or truck is the ease of cleaning and water infiltration of walls outside as well as inside by washing down to remove dirt, grease & food splatter. Thus to keeping the HD inspector happy because the kitchen is clean.

You insist on applying residential building code for wood framed & sheeted walls to that of mobile kitchen construction. It doesn't apply, water vapor (cooking steam & latent vapor) is removed by the exhaust fans and by the AC when in use.

You insist on applying residential building code for wood framed & sheeted walls to that of mobile kitchen construction. It doesn't apply, water vapor (cooking steam & latent vapor) is removed by the exhaust fans and by the AC when in use.